Mini Shell

"""
Use Consul K/V as a Pillar source with values parsed as YAML

:depends:  - python-consul

In order to use an consul server, a profile must be created in the master
configuration file:

.. code-block:: yaml

    my_consul_config:
      consul.host: 127.0.0.1
      consul.port: 8500
      consul.token: b6376760-a8bb-edd5-fcda-33bc13bfc556
      consul.scheme: http
      consul.consistency: default
      consul.dc: dev
      consul.verify: True

All parameters are optional.

The ``consul.token`` requires python-consul >= 0.4.7.

If you have a multi-datacenter Consul cluster you can map your ``pillarenv``
entries to your data centers by providing a dictionary of mappings in
``consul.dc`` field:

.. code-block:: yaml

    my_consul_config:
      consul.dc:
        dev: us-east-1
        prod: us-west-1

In the example above we specifying static mapping between Pillar environments
and data centers: the data for ``dev`` and ``prod`` Pillar environments will
be fetched from ``us-east-1`` and ``us-west-1`` datacenter respectively.

In fact when ``consul.dc`` is set to dictionary keys are processed as regular
expressions (that can capture named parameters) and values are processed as
string templates as per PEP 3101.

.. code-block:: yaml

    my_consul_config:
      consul.dc:
        ^dev-.*$: dev-datacenter
        ^(?P<region>.*)-prod$: prod-datacenter-{region}

This example maps all Pillar environments starting with ``dev-`` to
``dev-datacenter`` whereas Pillar environment like ``eu-prod`` will be
mapped to ``prod-datacenter-eu``.

Before evaluation patterns are sorted by length in descending order.

If Pillar environment names correspond to data center names a single pattern
can be used:

.. code-block:: yaml

    my_consul_config:
      consul.dc:
        ^(?P<env>.*)$: '{env}'

After the profile is created, configure the external pillar system to use it.
Optionally, a root may be specified.

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config

    ext_pillar:
      - consul: my_consul_config root=salt

Using these configuration profiles, multiple consul sources may also be used:

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config
      - consul: my_other_consul_config

Either the ``minion_id``, or the ``role``, or the ``environment`` grain  may be used in the ``root``
path to expose minion-specific information stored in consul.

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config root=salt/%(minion_id)s
      - consul: my_consul_config root=salt/%(role)s
      - consul: my_consul_config root=salt/%(environment)s

Minion-specific values may override shared values when the minion-specific root
appears after the shared root:

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config root=salt-shared
      - consul: my_other_consul_config root=salt-private/%(minion_id)s

If using the ``role`` or ``environment`` grain in the consul key path, be sure to define it using
`/etc/salt/grains`, or similar:

.. code-block:: yaml

    role: my-minion-role
    environment: dev

It's possible to lock down where the pillar values are shared through minion
targeting. Note that double quotes ``"`` are required around the target value
and cannot be used inside the matching statement. See the section on Compound
Matchers for more examples.

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config root=salt target="L@salt.example.com and G@osarch:x86_64"

The data from Consul can be merged into a nested key in Pillar.

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config pillar_root=consul_data

By default, keys containing YAML data will be deserialized before being merged into Pillar.
This behavior can be disabled by setting ``expand_keys`` to ``false``.

.. code-block:: yaml

    ext_pillar:
      - consul: my_consul_config expand_keys=false

"""

import logging
import re

import salt.utils.minions
import salt.utils.yaml
from salt.exceptions import CommandExecutionError
from salt.utils.dictupdate import update as dict_merge

try:
    import consul

    if not hasattr(consul, "__version__"):
        consul.__version__ = (  # Some packages has no version, and so this pillar crashes on access to it.
            "0.1"
        )
except ImportError:
    consul = None

__virtualname__ = "consul"

# Set up logging
log = logging.getLogger(__name__)


def __virtual__():
    """
    Only return if python-consul is installed
    """
    return __virtualname__ if consul is not None else False


def ext_pillar(minion_id, pillar, conf):  # pylint: disable=W0613
    """
    Check consul for all data
    """
    opts = {}
    temp = conf
    target_re = re.compile('target="(.*?)"')
    match = target_re.search(temp)
    if match:
        opts["target"] = match.group(1)
        temp = temp.replace(match.group(0), "")
        checker = salt.utils.minions.CkMinions(__opts__)
        _res = checker.check_minions(opts["target"], "compound")
        minions = _res["minions"]
        log.debug("Targeted minions: %r", minions)
        if minion_id not in minions:
            return {}

    root_re = re.compile(r"(?<!_)root=(\S*)")  # pylint: disable=W1401
    match = root_re.search(temp)
    if match:
        opts["root"] = match.group(1).rstrip("/")
        temp = temp.replace(match.group(0), "")
    else:
        opts["root"] = ""

    pillar_root_re = re.compile(r"pillar_root=(\S*)")  # pylint: disable=W1401
    match = pillar_root_re.search(temp)
    if match:
        opts["pillar_root"] = match.group(1).rstrip("/")
        temp = temp.replace(match.group(0), "")
    else:
        opts["pillar_root"] = ""

    profile_re = re.compile(r"(?:profile=)?(\S+)")  # pylint: disable=W1401
    match = profile_re.search(temp)
    if match:
        opts["profile"] = match.group(1)
        temp = temp.replace(match.group(0), "")
    else:
        opts["profile"] = None

    expand_keys_re = re.compile(
        "expand_keys=False", re.IGNORECASE
    )  # pylint: disable=W1401
    match = expand_keys_re.search(temp)
    if match:
        opts["expand_keys"] = False
        temp = temp.replace(match.group(0), "")
    else:
        opts["expand_keys"] = True

    client = get_conn(__opts__, opts["profile"])

    role = __salt__["grains.get"]("role", None)
    environment = __salt__["grains.get"]("environment", None)
    # put the minion's ID in the path if necessary
    opts["root"] %= {"minion_id": minion_id, "role": role, "environment": environment}

    try:
        pillar_tree = fetch_tree(client, opts["root"], opts["expand_keys"])
        if opts["pillar_root"]:
            log.debug(
                "Merging consul path %s/ into pillar at %s/",
                opts["root"],
                opts["pillar_root"],
            )

            pillar = {}
            branch = pillar
            keys = opts["pillar_root"].split("/")

            for i, k in enumerate(keys):
                if i == len(keys) - 1:
                    branch[k] = pillar_tree
                else:
                    branch[k] = {}
                    branch = branch[k]
        else:
            pillar = pillar_tree
    except KeyError:
        log.error("No such key in consul profile %s: %s", opts["profile"], opts["root"])
        pillar = {}

    return pillar


def consul_fetch(client, path):
    """
    Query consul for all keys/values within base path
    """
    # Unless the root path is blank, it needs a trailing slash for
    # the kv get from Consul to work as expected
    return client.kv.get("" if not path else path.rstrip("/") + "/", recurse=True)


def fetch_tree(client, path, expand_keys):
    """
    Grab data from consul, trim base path and remove any keys which
    are folders. Take the remaining data and send it to be formatted
    in such a way as to be used as pillar data.
    """
    _, items = consul_fetch(client, path)
    ret = {}
    has_children = re.compile(r"/$")

    log.debug("Fetched items: %r", items)

    if items is None:
        return ret
    for item in reversed(items):
        key = re.sub(r"^" + re.escape(path) + "/?", "", item["Key"])
        if key != "":
            log.debug("path/key - %s: %s", path, key)
            log.debug("has_children? %r", has_children.search(key))
        if has_children.search(key) is None:
            ret = pillar_format(ret, key.split("/"), item["Value"], expand_keys)
            log.debug("Fetching subkeys for key: %r", item)

    return ret


def pillar_format(ret, keys, value, expand_keys):
    """
    Perform data formatting to be used as pillar data and
    merge it with the current pillar data
    """
    # if value is empty in Consul then it's None here - skip it
    if value is None:
        return ret

    # If value is not None then it's a string
    # YAML strips whitespaces unless they're surrounded by quotes
    # If expand_keys is true, deserialize the YAML data
    if expand_keys:
        pillar_value = salt.utils.yaml.safe_load(value)
    else:
        pillar_value = value

    keyvalue = keys.pop()
    pil = {keyvalue: pillar_value}
    keys.reverse()
    for k in keys:
        pil = {k: pil}

    return dict_merge(ret, pil)


def get_conn(opts, profile):
    """
    Return a client object for accessing consul
    """
    opts_pillar = opts.get("pillar", {})
    opts_master = opts_pillar.get("master", {})

    opts_merged = {}
    opts_merged.update(opts_master)
    opts_merged.update(opts_pillar)
    opts_merged.update(opts)

    if profile:
        conf = opts_merged.get(profile, {})
    else:
        conf = opts_merged

    params = {}
    for key in conf:
        if key.startswith("consul."):
            params[key.split(".")[1]] = conf[key]

    if "dc" in params:
        pillarenv = opts_merged.get("pillarenv") or "base"
        params["dc"] = _resolve_datacenter(params["dc"], pillarenv)

    if consul:
        # Sanity check. ACL Tokens are supported on python-consul 0.4.7 onwards only.
        if consul.__version__ < "0.4.7" and params.get("target"):
            params.pop("target")
        return consul.Consul(**params)
    else:
        raise CommandExecutionError(
            "(unable to import consul, "
            "module most likely not installed. Download python-consul "
            "module and be sure to import consul)"
        )


def _resolve_datacenter(dc, pillarenv):
    """
    If ``dc`` is a string - return it as is.

    If it's a dict then sort it in descending order by key length and try
    to use keys as RegEx patterns to match against ``pillarenv``.
    The value for matched pattern should be a string (that can use
    ``str.format`` syntax togetehr with captured variables from pattern)
    pointing to targe data center to use.

    If none patterns matched return ``None`` which meanse us datacenter of
    conencted Consul agent.
    """
    log.debug("Resolving Consul datacenter based on: %s", dc)

    try:
        mappings = dc.items()  # is it a dict?
    except AttributeError:
        log.debug("Using pre-defined DC: '%s'", dc)
        return dc

    log.debug("Selecting DC based on pillarenv using %d pattern(s)", len(mappings))
    log.debug("Pillarenv set to '%s'", pillarenv)

    # sort in reverse based on pattern length
    # but use alphabetic order within groups of patterns of same length
    sorted_mappings = sorted(mappings, key=lambda m: (-len(m[0]), m[0]))

    for pattern, target in sorted_mappings:
        match = re.match(pattern, pillarenv)
        if match:
            log.debug("Matched pattern: '%s'", pattern)
            result = target.format(**match.groupdict())
            log.debug("Resolved datacenter: '%s'", result)
            return result

    log.debug(
        "None of following patterns matched pillarenv=%s: %s",
        pillarenv,
        ", ".join(repr(x) for x in mappings),
    )